One tension device of the type with which the present invention is concerned is disclosed in U.S. Pat. No. 4,472,162 entitled BELT TENSIONER whose Abstract states "A tensioning device is provided with an adjusting element that is adapted to be affixed to the tensioning device after the tension spring therein has been tensioned." In this device the tension spring has a stationary part in a recess of a multi-part support. In addition, a pot shaped sheet metal body has a projection engaging a support plate to prevent turning thereof. As a result the tension of the spring and the working point is fixed and cannot be adjusted. Since the spring that is used is subject to large variations in its spring force due to its preparation or as a result of defects in the material, great variations in the characteristics of the devices can be expected in mass production.
For this reason, as proposed in German Patent Application P 39 08 817.0, the tension device, after its preparation, is pretensioned to the value of the later desired workpoint, and at this position is positioned with respect to marks or the like which permit reproducing the position with a defined tension force. The known device are not suitable, however, if the tension device is to be provided with an arrangement for limiting the turning region or is to be provided with other features which proscribe one orientation, without additional arrangements.